Calculation of single-layer dielectric coatings for antireflection in a given range of angles of incidence

In this work, the problem of antireflection a single-layer magneto-dielectric system is formulated when a plane electromagnetic wave passes through it in the range of angles of incidence, and necessary and sufficient conditions for the existence of solutions to this problem are obtained

Matrix Dielectric Permittivity for Enhanced Formation Evaluation

Modern dielectric tools are often run to obtain fundamental formation properties, such as remaining oil saturation, water-filled porosity, and brine salinity. Techniques to extract more challenging reservoir petrophysical properties like Archie m and n parameters are also emerging. The accuracy and representativeness of the obtained petrophysical parameters depend on the input parameter accuracy, such as matrix permittivity. In carbonates, matrix permittivity is known to vary over a wide range, for example, limestone matrix permittivity reported in the literature ranges from 7.5 to 9.2. The main objective of the current study is to reduce matrix dielectric permittivity uncertainty for enhanced formation evaluation in carbonate reservoirs. All dielectric measurements were conducted on 1.5 in. carbonate plug samples by means of a coaxial reflection probe with a range of frequency between 10 MHz and 1 GHz. To calculate matrix mineral dielectric permittivity, sample porosity must be obtained. Stress-corrected helium porosity from routine core analysis is used and samples mineralogy and chemical composition are measured by X-Ray diffraction. Dielectric system calibration is done by utilizing several well-characterized standards with known dielectric properties. Calcite and dolomite matrix permittivity are assessed by laboratory measurements. Results of this study and based on data from 180 core plugs allowed to assess the validity of the defined errors by statistical analysis, resulting in much reduced uncertainties in carbonate rock matrix dielectric permittivity; thus enhancing formation evaluation using dielectric measurements. The current study provides better control on dielectric permittivity values used in dielectric log interpretation for limestone formations. Such knowledge will provide better confidence in interpreted data such as water-filled porosity, flushed zone salinity and water phase tortuosity.

A floating top-electrode electrowetting-on-dielectric system

A novel device configuration for an electrowetting-on-dielectric system with a floating top-electrode, which provides possibilities to enable a true lab-on-a-chip.

Symmetrized Maxwell–Garnett Approximation as an Effective Method for Studying Nanocomposites

The symmetrized Maxwell-Garnett (SMG) approximation is considered as the most optimal method of an effective medium for the description of nanocomposite structures. This approximation takes into account the microstructure of the sample, which makes it possible to calculate the metal-dielectric system. Thus, SMG describes with good accuracy the structure of the nanocomposite. Besides, this approximation is applicable for granular alloys consisting of metal components. As a result, this technique can be considered as a universal approximation to describe a wide class of nanostructured materials. At the same time, this article discusses various methods of effective environment. In these methods, the metal component of nanocomposites and the dielectric matrix are replaced by an effective medium with effective permittivity εeff. It is necessary that the particles (granules) in such structures be small in comparison with the wavelength of electromagnetic radiation incident on the sample. Based on this, the spectral dependences of the transverse Kerr effect (TKE) in magnetic nanocomposites were calculated with (CoFeZr)(Al2O3) structure as an example at different concentrations of the magnetic component. The simulation was carried out at small and large concentrations (below and above the percolation threshold). The spectral dependences were obtained taking into account the form factor of nanoparticles and the quasi-classical size effect. Besides, the authors note and discuss in this paper the contribution of various mechanisms that affect the type of spectra of the transverse Kerr effect. Using the symmetrized Maxwell-Garnett approximation, the effective values of the granule size of the nanocomposites under study were found, and the tensor of effective dielectric permittivity (TEDP) was calculated. The obtained TEDP values allowed to simulate the spectral dependences of the magneto-optical transverse Kerr effect. The authors discuss and draw conclusions about the features of the obtained spectral dependences in both the visible and infrared regions of the spectrum. In addition, the practical and fundamental importance of the obtained results is noted. The importance of effective medium methods for the study of optical, transport and magneto-optical properties of magnetic nanocomposites is shown.